1. Field of the Invention
The present invention relates to a system and method for the detection of one or more locator units in the proximity of a transmitter system. More specifically, the present invention relates to a system that detects the proximity of a person or machine carrying the locator to a dangerous machine configured with the driver system, and determines the exact location of that person or machine and if that person or machine is close enough to be in danger. The system and method according to the present invention can also be used in a vehicle to vehicle collision avoidance setting where one or more drivers are positioned on a primary vehicle and a locator is positioned on each of one or more secondary vehicles. The proximity detection system and method of the present invention can be used on any mobile equipment, and is not intended to be limited to the mining industry.
2. Description of Prior Art
Industrial machines may be necessarily large and powerful. For example, continuous mining machines may be 40 feet long, 10-12 feet wide, 3-4 feet tall, and weigh 40 tons. Such machines have injured or killed people while being operated. For example, in “tramming,” a continuous mining machine mounted on tracks is moved from one location to another in confined spaces at relatively high speeds and can turn or change directions fast enough to pin an operator against a rib (i.e., wall) of the mining space.
With respect to the environment, it may not be possible to set up traditional operator protection systems, such as light fences or guard rails, because the environment is generally unstructured (e.g., mining machines create the environment as they operate). Further, such environments are often noisy, dusty and wet.
A transducer, speaker or microphone that is exposed to such an environment is not likely to survive or function properly. For example, sonar and laser time-of-flight sensors exposed to such an environment will become dirty and non-operational very quickly. Further, such sensors have difficulty distinguishing between a person and other structural components in the environment, such as the wall of the mining space.
With respect to radio time-of-flight sensors, such as radar, while the components may be more durable in the environment the relatively short distances (e.g., two feet to 50 feet) between the operator and the machine make such sensors impractical and unreliable. Further, the requirement of a relatively large radio dish or directional radio antenna is impractical.
Alternatively, other systems utilize a magnetic field generator on the machine and a magnetic field sensor carried by the operator. The magnetic field generator creates a magnetic field around the machine. The magnetic field sensor senses the strength of the magnetic field and then relays the strength of the field by radio back to the machine. If the operator is determined to be too close to the machine, the machine is shut down. However, this system is limited to a substantially circular safety perimeter around the machine, so there is no ability to arbitrarily define a safety perimeter because there is no way to determine an exact location of the operator with respect to the machine. Thus, the safety perimeter must be set to a radius that includes a safety margin from the most distant points of concern of the machine, leaving areas that are safe inside of the safety perimeter. This becomes a nuisance because it prevents the operator from operating in areas that are safe and effective because of the lack of geometric control of the safety perimeter.
In the invention disclosed in U.S. Pat. No. 8,289,170, applicants herein invented a system that could determine the location of the operator with respect to the machine and, if necessary, shut the machine down without requiring any structure in the environment. That system included transmitters on the operators and a plurality of receiver units on the machine. One disadvantage of this system is that, because the transmitters are on the operators, not the machine, power and range are necessarily limited.
Thus, what is needed is a system for determining the location of the operator with respect to the machine wherein an encoded signal of greater power can be transmitted to increase the area in which an operator can be detected. Further, there is needed a system where the range and shape of the encoded signal can be customized and modified to suit the particular needs of the machinery being used. Advantageously, with such a system, the operator will learn to maintain a safe distance from the machine to be efficient in their job.